Not a very exciting realisation, but an annoying one:

$ irb
>> class A
>>   def self.meth; puts "class method!"; end
>> end

>> A.meth()
class method!

>> A.new().meth()
NoMethodError: undefined method `meth' for #<A:0x5ad160>
	from (irb):11

ick…

(sadly enough, most of my posts tagged “ruby” would be equally well tagged as “things that suck in ruby”)